Bottle base



FIG. 1 is a left side top perspective view of the bottle base showing my new design;

FIG. 2 is a left side elevational view thereof which is a mirror image of the right side, front, and back views thereof;

FIG. 3 is a top plan view thereof; and,

FIG. 4 is a bottom plan view thereof.

The broken line showing of portions of the bottle is included for the purpose of illustrating environmental structure and forms no part of the claimed design. 

The ornamental design for a bottle base, as shown and described. 